Closing arguments were underway Monday in the trial of a key defendant in a San Francisco Chinatown organized crime probe that also ensnared a state senator.

Raymond "Shrimp Boy" Chow is charged in U.S. District Court with racketeering and murder.

Prosecutors said Chow took over a Chinese fraternal group after having its previous leader killed and ran an enterprise that engaged in drug trafficking, money laundering and the sale of stolen cigarettes and alcohol. He is also accused of a second killing.

The courtroom was packed Monday as Assistant U.S. Attorney Susan Badger addressed the jurors. In an argument that's lasted at least one hour, she painted Chow as a cold-blooded killer and skilled liar, and not the smiling reformed former bad boy he claimed to be.

"He is not the victim here," she said. "He is not the world's most misunderstood criminal."

Chow's lead attorney, J. Tony Serra, will offer his closing argument next.

The investigation was spearheaded by an undercover FBI agent posing as a member of an East Coast crime syndicate, who testified that he spent hours with Chow and people connected to him at fancy restaurants and nightclubs, recording many of their conversations.

The agent, who testified under the pseudonym David Jordan to protect his identity, said Chow tried to distance himself from any criminal activity during the probe, but repeatedly accepted money after introducing the agent to money launderers.

The probe led to the indictment of more than two dozen people in 2014 and the subsequent racketeering conviction of state Sen. Leland Yee.

Chow testified to dealing drugs and getting involved in a street gang, but said after engaging in meditation, he decided to renounce criminal activity and focused instead on writing his biography.

He denied involvement in both of the slayings, and said the agent gave him the money because the agent was looking out for him, not in exchange for criminal activity.

Chow said he didn't want to know whether the agent was involved in illegal activity, so he would walk away from conversations the agent engaged in. Those conversations included discussions about money laundering, according to previous testimony.